Cement particles-containing grouting composition are used by being injected into spaces between particles of grounds or rock cracks for water shutoff, prevention of liquefaction, improvement of soft grounds, or prevention of leakage of toxic substances. Such compositions have been widely used in foundation works in civil engineering and construction. Such compositions have been used for ground improvement (ground reinforcement) and water shutoff at the time of construction of barrage, tunnel, subway, waterworks and sewer, and the like. Slurry cement grouting compositions obtained by mixing a cement grout with water and stirring the mixture have been used as such cement grouting compositions. In this case, dispersants are used in order to enhance dispersibility of the cement particles, thereby improving performances thereof as a grouting composition. Slurries obtained by mixing a cement grout, a dispersant, and water with each other and stirring the mixture have been used. Examples of such a cement grout include Ordinary Portland cement, High early strength Portland cement, blast furnace cement, colloid cement, and ultrafine particle cement. The particle diameter of the cement grout is important for performances of the cement grouting compositions. The injectability of the composition can be improved by reducing the particle diameter, generally. The ultrafine particle cement is the most excellent in injectability and useful, among the cement grouts.
If the slurry ultrafine particle cement grouting composition is used, the dispersant is essential in order to prevent aggregation of the particles in the cement grout and thereby improve and maintain the performances of the grouting composition. Naphthalene dispersants used as a cement dispersant have been used, because the ultrafine particle cement grouting composition contains a cement component. Normal type naphthalene dispersants and retardation type naphthalene dispersants have been mainly used as such naphthalene dispersants. The normal type naphthalene dispersants have been desired to be more excellent in dispersibility. The retardation type naphthalene dispersants have been desired to be more excellent by reducing the setting retardation. In a cement dispersant field, polycarboxylic acid dispersants have been used as cement dispersants with high dispersion functions. However, for ultrafine particle cement grouting compositions, the polycarboxylic acid dispersants were inferior to naphthalene dispersants in permeability, permeability retainability, and setting characteristics. That is, advantages of the polycarboxylic acid dispersants have not been recognized conventionally even if the polycarboxylic acid dispersants used in the cement dispersant field are used for the ultrafine particle cement grouting composition.
For example, Japanese Kokai Publication No. Hei-08-319484, Japanese Kokai Publication No. Hei-08-41455, Japanese Kokai Publication No. Hei-11-116316, and Japanese Kokai Publication No. 2004-231884 disclose technologies of using a conventional polycarboxylic acid dispersant for an ultrafine particle cement grouting composition. However, in these technologies, polycarboxylic acid dispersants which are commercially available in the cement dispersant field are used. No polycarboxylic acid dispersants which can exhibit sufficient performances in the ultrafine particle cement grouting composition field, in comparison to the naphthalene dispersants, have been known. That is, the grouting compositions contain cement, but are used under the condition that a ratio of water to cement is higher than that in concrete or mortar. Further, the particle size of the cement particles contained in the compositions is largely different from that of the cement particles contained in concrete or mortar. Therefore, sufficient performances were not obtained if the technologies of the polycarboxylic acid dispersants in a conventional cement dispersant field are applied for the grouting compositions. Therefore, the ultrafine particle grouting compositions have been desired to sufficiently exhibit various characteristics needed as an ultrafine particle grouting composition, such as permeation performances, permeation retainability performances, and setting characteristics, by taking advantage of the polycarboxylic acid dispersants.
Mixtures which contains Portland cement or Portland cement clinker (hereinafter, referred to as cement clinker), blast furnace slag and gypsum and has the maximum particle diameter of about 10 to 16 μm have been used as conventional ultrafine particle cement grouts.
Japanese Patent No. 3423913 discloses, for example, ultrafine particle cement composed of particles in which an amount of particles with about 2 μm or less and the particle size are specified for improving dispersibility or reducing an apparent coarsening of the particles caused by aggregation. Such ultrafine particle cement within a specific particle size range has improved injectability in comparison with that of the conventional ultrafine particle cement. However, such cement can not be injected in some cases because of the particle diameter, depending on spaces between particles or rock cracks into which the cement is injected. Accordingly, an ultrafine particle cement grouting composition excellent in injectability and capable of corresponding to various grounds or rocks has been desired.
Ultrafine particle cements with a particle diameter smaller than necessary, for example, super ultrafine particle cements having a particle diameter smaller than that of the ultrafine particle cements have a strong aggregation function. Therefore, aggregation between the particles is found even in dry state, and a phenomenon in which an aggregation rate in a slurry is extremely high is observed. Accordingly, the particles in the slurry tend to disperse insufficiently, and the aggregation accelerates the apparent coarsening of the particles. Use of such a slurry as a grout causes reduction in injectability (for example, referring to Akira Mori, Masahito Tamura, Yasushi Aoki, “Permeability limit of ultrafine particle grout”, Japan Society of Civil Engineers collected papers, No. 426/V-14, pp 237-240 (1991. 2))
Because of the above-mentioned circumstances, Japanese Kokai Publication No. Hei-03-26783 discloses a high-pressure dispersion treatment method or Japanese Kokai Publication No. 2000-70700 discloses a method of removing aggregated particles after ultrasonic treatment, in order to enhance the dispersibility of the cement particles and thereby improve the injectability. However, in these methods, particular devices are needed and the production lines are complicated, or the particles tend to be aggregated again after the dispersion treatment. Therefore, these methods have room for improvement in order to enhance the dispersion retainability and the like and thereby improve the injectability. The method of removing aggregated particles after ultrasonic treatment is also insufficient in injection efficiency because slurry which should be discarded is generated. Therefore, practical application of an ultrafine particle cement grout-containing grouting composition expected to have extremely high injectability is needed. There is room for improvement in order to improve the dispersibility or the dispersion retainability of the ultrafine particle cement grout by an industrially simple method, and to provide a composition which is advantageous also in terms of injection efficiency.